Abstract
BackgroundExercise stress tests are commonly used in clinical settings to monitor the functional state of the heart and vasculature. Large artery stiffness is one measure of arterial function that can be quantified noninvasively during exercise stress. Changes in proximal pulmonary artery stiffness are especially relevant to the progression of pulmonary hypertension (PH), since pulmonary artery (PA) stiffness is the best current predictor of mortality from right ventricular failure.MethodsCardiovascular magnetic resonance (CMR) was used to investigate the effect of exercise stress on PA pulse wave velocity (PWV) and relative area change (RAC), which are both non-invasive measures of PA stiffness, in healthy subjects. All 21 subjects (average age 26 ± 4 years; 13 female and 8 male) used a custom-made MR-compatible stepping device to exercise (two stages of mild-to-moderate exercise of 3–4 min duration each) in a supine position within the confines of the scanner. To measure the cross-sectional area and blood flow velocity in the main PA (MPA), two-dimensional phase-contrast (2D-PC) CMR images were acquired. To measure the reproducibility of metrics, CMR images were analyzed by two independent observers. Inter-observer agreements were calculated using the intraclass correlation and Bland-Altman analysis.ResultsFrom rest to the highest level of exercise, cardiac output increased from 5.9 ± 1.4 L/min to 8.2 ± 1.9 L/min (p < 0.05), MPA PWV increased from 1.6 ± 0.5 m/s to 3.6 ± 1.4 m/s (p < 0.05), and MPA RAC decreased from 0.34 ± 0.11 to 0.24 ± 0.1 (p < 0.05). While PWV also increased from the first to second exercise stage (from 2.7 ± 1.0 m/s to 3.6 ± 1.4 m/s, p < 0.05), there was no significant change in RAC between the two exercise stages. We found good inter-observer agreement for quantification of MPA flow, RAC and PWV.ConclusionThese results demonstrate that metrics of MPA stiffness increase in response to acute moderate exercise in healthy subjects and that CMR exercise stress offers great potential in clinical practice to noninvasively assess vascular function.
Highlights
Exercise stress tests are commonly used in clinical settings to monitor the functional state of the heart and vasculature
We investigated the effect of exercise stress on non-invasive, cardiovascular magnetic resonance (CMR) metrics of main PA (MPA) stiffness
At the second stage of exercise (ST2, 45 W) heart rate further increased significantly by 15 % leading to a total increase of 50 % compared with rest
Summary
Exercise stress tests are commonly used in clinical settings to monitor the functional state of the heart and vasculature. In which a subject’s heart rate and cardiac output (CO) are increased by physical exercise, are often conducted clinically to monitor the functional state of the heart and vasculature. When non-invasive imaging is performed in conjunction with exercise stress, echocardiography and single photon emission computed tomography (SPECT) are most often used to assess parameters such as ventricular function and exerciseinduced hemodynamic changes. Echocardiography of the pulmonary circulation is challenging due to the difficulties in obtaining an acceptable acoustic window, aligning the ultrasound beam with the flow direction [1] and short penetration depth [2]. Cardiovascular magnetic resonance (CMR) is capable of obtaining anatomical data at arbitrary imaging planes and measuring flow in any direction at the expense of longer scan times. The stress condition induced by physical exercise better represents cardiovascular stresses experienced in daily life
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